The effect of poly[styrene-b-(ethylene-co-butylene)-b-styrene] on dielectric, thermal, and morphological characteristics of polypropylene/silica nanocomposites

Abstract

The effect of poly[styrene-b-(ethylene-co-butylene)-bstyrene] (SEBS) copolymer on the thermal and dielectric properties of polypropylene (PP)-nanosilica (NS) composites in relation with morphological aspects revealed by atomic force microscopy (AFM) was investigated in this article. SEBS hindered the crystallization process of PP in PP/NS composites, leading to a smaller degree of crystallinity and lower perfection of crystalline structure. Broader lamellar thickness distribution was obtained in nanocomposites containing SEBS. Almost two times higher dielectric loss as compared to PP reference and two relaxation processes were detected in e 00 r (f) curves of nanocomposites. The first peak, in the same frequency domain as for the references, was assigned to a-relaxation of polymer components together with interfacial polarization. The relaxation time follows the Arrhenius law with an activation energy of 80-90 kJ/mol. For the second process, the temperature dependence of the relaxation times obeyed the VFT equation. The dielectric changes following the incorporation of SEBS support its tendency to hinder the motional processes in PP, in accordance with DSC results. A smooth transition from a phase rich in SEBS to one containing mainly PP was detected in the AFM image of the composite with the larger amount of SEBS, emphasizing the good compatibility at the PP/SEBS interface.

On the effect of functionalizer chain length and water content in polyethylene/silica nanocomposites: Part I — Dielectric properties and breakdown strength

“…Taking all of these together, it is convenient to discuss them in terms of two broad relaxation peaks which, for the ambient nanocomposite samples, equate to a minor peak at ~1 Hz and a major peak at ~1 kHz. This behavior is very different from that seen in the case of the unfilled polyethylene, which indicates that the causal effects are again a consequence of the inclusion of the nanoparticles [8,9]. With increasing water content (dried → ambient → wet samples), the major peak shifts from <0.1 Hz to 100 kHz and also increases somewhat in magnitude from 0.22 to 0.32; the minor peak also shifts to higher frequencies in a similar manner.…”

“…Whilst the addition of a nanofiller leads to two characteristic loss peaks and an increase in permittivity at low frequencies [8,9,12,16,18,21,22], in cases where the nanofiller is well dispersed, this is not observed. Instead, the dielectric loss increases in a similar manner to that in comparable micro-filled systems [15,[16][17]20].…”

“…Since the attractive properties of nanodielectrics have generally been ascribed to the large specific interfacial area that exists within such systems and the subsequent formation of interphases [6,7], achieving good nanoparticle dispersion and avoiding particle aggregation is generally considered to be key, but is very difficult to achieve consistently [8][9][10][11][12]. Consequently, when the breakdown strength of a nanocomposite is compared with that of an identical polymer without nanofiller, examples can be found where the addition of the nanofiller reduced the breakdown strength [13,14], where no change in breakdown strength was seen [15] or where increased breakdown strength occurred [16,17].…”

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

“…Low frequency relaxation processes can be associated with pseudo-DC conduction and the MaxwellWagner effect, which is associated with the trapping of charges either at internal boundaries within materials or at the external electrodes that contact the sample [46]. Here, nanoparticle/matrix interfaces are of considerable importance in this respect and previous studies of nanocomposites have demonstrated that interfacial accumulation of water molecules can be a major contributing factor to the observed low frequency dielectric response [7,45,47]. In contrast, AlO10 shows two mid frequency relaxation peaks (Fig.…”

Influence of filler/matrix interactions on resin/hardener stoichiometry, molecular dynamics, and particle dispersion of silicon nitride/epoxy nanocomposites

“…This increase in 00 r at low frequencies might be due to a higher DC conductivity of these samples or might be the high frequency tail of a relaxation that peaks at a frequency below our accessible range. Many studies have shown that the addition of nanoparticles imparts a new mid-or lowfrequency relaxation peak that moves to higher frequencies with increasing temperature [36,52] or with absorbed water [53][54][55]. Related to the materials considered here, Hosier [56] has recently reported that the addition of Si 3 N 4 nanoparticles into a polyethylene matrix causes a new relaxation that shifts to higher frequency with higher water uptake; Yeung [36] has also observed a similar feature that peaks at higher frequencies for higher temperatures, for the same epoxy matrix when filled with nanosilica.…”